I tried to select the entire section "Language feature" in https://en.wikipedia.org/wiki/Delegation_(programming) with my mouse, but could not because the selection restricts itself to just the <source> code block when I drag downwards to include the <source> code block in my selection.
(With the keyboard, it's even worse because only the section heading can be selected, but that's a different bug.)
It works for me. You have to drag over the entire block to select it, but it works fine. Does it work differently for you?
Unfortunately closing this Phabricator task as no further information has been provided.
@Greenrd: After you have provided the information asked for and if this still happens, please set the status of this task back to "Open" via the Add Action... → Change Status dropdown. Thanks!